An old man with a tengu mask named Sakonji Urokodaki receives a letter from a crow sent by Giyu Tomioka. Giyu states that a young boy whose family was slaughtered by a Demon is on his way to meet the old man. The boy's sister was turned into a Demon, however, Giyu states that he believes she will not harm humans. He also observes that the boy possesses the same particularly good sense of smell as Sakonji and requests Sakonji train him, given he could potentially become the old man's successor.
After this memory, Sakonji now looks at Tanjiro who is about to finish off the Temple Demon with a small knife. Tanjiro notes that he did not notice the man's presence at all as his footsteps were so light. The boy requests Sakonji to tell him how he should go about killing the Demon, to which Sakonji replies that he should figure it out himself.
Tanjiro spots a rock nearby and decides that instead of the knife, he could use the rock to crush the Demon's skull repeatedly till it dies. However, before he is able to act, he feels sympathy for the Demon's suffering and tries to think of a less painful method to kill it in one blow. Upon detecting Tanjiro's hesitation, Sakonji realizes Tanjiro has overflowing empathy and kindness even towards a Demon and berates Giyu in his mind, telling him that this boy isn't a suitable candidate.
As Tanjiro continues hesitating, the first rays of sunlight appear and instantly burn the Demon to ashes, causing Tanjiro to realize why Nezuko dislikes the sun so much. Meanwhile, Sakonji gives the victims a proper burial. When Tanjiro approaches the man, he introduces himself as Sakonji Urokodaki. Before Tanjiro has the opportunity to properly introduce himself and his sister, Sakonji questions Tanjiro what he would do if his sister eats a human being. Tanjiro pauses before answering and Sakonji slaps him, reprimanding him for being too hesitant. He tells Tanjiro that in the event his sister eats a human being, he should kill her and then kill himself—the kind of resolve that Tanjiro needs if he wants to bring along his Demon sister on his journey. Tanjiro replies that he understands, to which Sakonji responds he should bring Nezuko and follow him for a test.
Sakonji's speed makes it difficult for Tanjiro to follow after him. As he is running, Tanjiro feels sorry for Nezuko that she is being jostled around in the basket. He recalls that Nezuko has always been patiently enduring suffering throughout her whole life. For the sake of their siblings, Nezuko had refused to buy new clothes in order to buy more food for them instead. Tanjiro firmly decides that he will turn her back into a human and give everything to her to make up for the things he is unable to do now for his deceased siblings.
They soon reach a hut and Tanjiro breathlessly asks whether he had passed the test. Sakonji tells him that the test has only just begun and orders him to ascend the mountain. Upon hearing these words, Tanjiro is dumbfounded but complies.
After leaving Nezuko in the hut, the pair head up. Tanjiro feels that his legs are tired to the point where he is unable to move them and his head was dizzy. Upon reaching a certain point, Sakonji tells Tanjiro that the test is for him to reach the bottom of the mountain to where his house is, and unlike with the Temple Demon, he will not wait until dawn. Sakonji then subsequently leaves.
Surprised that the test is so simple, Tanjiro believes his sense of smell would make it a breeze and begins following Sakonji's scent. However, just as he takes a step, Tanjiro's foot gets caught in a trap that launches small rocks towards him. He then falls into a hidden pit, and, right after crawling out, triggers another trap that launches a log which hits him from behind.
Tanjiro then realizes that if he keeps getting caught in the traps, he would not be able to reach the foot of the mountain by dawn. Moreover, the air in this mountain is thinner than where he had lived before, causing him to have difficulty breathing. Feeling desperate, Tanjiro wonders if he could truly make it back in time. However, he steadies himself and tells himself that he must make it back. By adjusting his breathing and concentrating, he attempts to smell out the distinctly different human traps. Even so, he is not agile enough to avoid all of them.
Meanwhile, by the foot of the mountain, Sakonji places a blanket over the sleeping Nezuko. He suddenly hears some noise by his door and sees it open to reveal a very battered Tanjiro panting heavily. As he slumps down to the ground, Tanjiro states he successfully made it back.
As the morning sun begins to rise, Sakonji tells Tanjiro that he has now acknowledged him as his student.
Characters in Order of Appearance
- Tanjiro realizes Demons burn and turn into ash when exposed to sunlight.
- Sakonji challenges Tanjiro to determine if he'll train him.
- Tanjiro successfully passes Sakonji's test and the man accepts him as his student.